As a kind of semiconductor device, there is known a NAND type flash memory device having a three-dimensional structure. In the manufacture of this NAND type flash memory device having the three-dimensional structure, a deep hole is formed in a multilayered film, which is composed of alternately stacked two layers having different permittivities, by performing an etching process. This etching process is described in Patent Document 1.
To elaborate, in Patent Document 1, there is described a method of etching a multilayered film by exposing a processing target object having a mask on the multilayered film to plasma of a processing gas containing a HBr gas, a C4F8 gas and a BCl3 gas. In the method described in Patent Document 1, a polycrystalline silicon film of the multilayered film is etched by an active species generated from the HBr gas; a silicon oxide film of the multilayered film is etched by active species generated from the C4F8 gas; and a protective film generated from the BCl3 gas is deposited on a sidewall surface formed by the etching of the multilayered film. The protective film suppresses the multilayered film from being etched in a direction (i.e., a horizontal direction) orthogonal to a stacking direction (i.e., a vertical direction) of the multilayered film. Therefore, verticality of a space such as a hole formed in the multilayered film can be improved.
Patent Document 1: International Publication No. 2014/010499
In the etching method described in Patent Document 1, however, the size of the opening of the mask may become smaller, and, occasionally, the opening may be completely clogged. Further, it is still required to further improve the verticality of the space formed in the multilayered film by forming a stronger protective film.
Thus, in the present technical field, the clogging of the opening of the mask needs to be suppressed, and the verticality of the space formed in the multilayered film needs to be improved.